The purpose of this research study is to compare smokers with non-smokers in cardiovascular (i.e. blood pressure and heart activities) responses to stressors. An additional purpose is to compare, in women who are already taking oral contraceptives (i.e. birth control pills), two different types of commonly prescribed oral contraceptives: those containing the progesterone levengestrel or norethisterone versus those containing the progesterone desogestrel, gestodene or norgestimate, and how the combination of smoking and oral contraceptives use affects the cardiovascular system in women. The purpose is also to examine two different ways of administering Hormone Replacement Therapy (HRT) in postmenopausal women smokers. HRT is the administration of the female sex hormones, estrogen and progesterone, after women have reached menopause. This study will compare oral administration (by mouth) with transdermal administration (through the skin by wearing a skin patch) for effects on blood pressure and other cardiovascular measures.